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A331033 a(n) is the least k such that the denominator(sigma(sigma(k))/k) equals n. 2
1, 30, 3, 32, 5, 864, 7, 128, 9, 10, 11, 96, 13, 3570, 45, 256, 17, 216, 19, 40, 147, 22, 23, 6912, 25, 468, 567, 224, 29, 2520, 31, 416, 33, 374, 35, 147456, 37, 152, 117, 10800, 41, 102816, 43, 88, 135, 46, 47, 768, 49, 21000, 153, 52, 53, 6696, 165, 896, 171, 7424, 59, 36960 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
a(n) is the least k such that the A318060(k) equals n.
a(n) is divisible by n.
LINKS
PROG
(PARI) a(n) = my(k=n); while (denominator(sigma(sigma(k))/k) != n, k+=n); k;
CROSSREFS
Cf. A000203 (sigma), A051027 (sigma(sigma)), A318060.
Sequence in context: A040885 A040887 A040888 * A040889 A307026 A040882
KEYWORD
nonn
AUTHOR
Michel Marcus, Jan 08 2020
STATUS
approved

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Last modified September 12 01:49 EDT 2024. Contains 375842 sequences. (Running on oeis4.)